Rheostat



Nov. 19, 1935. F. w MCDoNi-:LL ET'AL 2,021,487

RHEOSTAT Filed April 12, 1934 l N l A wg? VcbfL. 0.5' 00dl MTORNEY Patented Nov. T19, 1935 UNITED STATES, PATENT oFFicE Application April 1a, 1934, serial No. '120,164

8 Claims.

This invention relates tothe design of a rheostat and has for one of its objects the design of a rheostat of the type suitable for mounting on mounting plates or panel boards which, by way of illus- 5 tration but not of limitation, may be found in radio receiving sets.

In rheostats of. the type heretofore referred to it has been the practice to use the control arm either directly or indirectly as a conductor of cur- 1o rent from one side of the circuit to the resistance winding element. In these prior art designs much difiiculty is encountered in making electrical connection through the rotating shaft and arm to the resistance winding. In certain,y cases iiexible cables are used in shunt to the arm, and springs are utilized to force the shaft endwise, so as to cause the arm-or an auxiliary vmember carrieddirectly thereby to firmly engage the resistance winding.

vIt is the principal object of our invention to provide a rheostat in which the dimculties of carrying the current through the shaft and rotating arm are entirely avoided by the complete elimination of the shaft andcontact-carrying arm from the rheostat circuit.

Another object of our invention is to provide a` new form of contact device which is self-aligningA on the resistancewginding. and a cooperating contact member, whereby good contact will always convolutionsfof the winding are not in exactly the same plane, or in the "plane of an associated con- 1 tact member which cooperates with the contact device carried by the movable arm.

` Another object of ur inventionisyto provide a contact device to be carried by the movable arm in such a manner that it may be quickly changed if desired.

Another object ofour invention is to provide mounting plate or panel.

Other ,and further objects will appear from the description taken in connection with the drawing wherein:

Figure l is a viewof the contact end of one form of our invention.

Figure 21s a side elevation of the rheostat be insured even" though the outer peripheries'of the Y improved meansfor mounting the rheostat on a' (Cl. .M1-56) forming part of ure 4.

Figure 6 is a perspective view tact members perl se.

Figure 'I is a perspective view of the holder and 5 the end o! the arm carrying the holder.

Figure 8 is a view similar tofFigurel but of a smaller and somewhat modified form of our invention. l

Figure 9 is a vertical sectional 'view through 10 .Figure 8.

Figure 10 is a perspective view of the holder and contact members used in the device shown in Figures 8 and 9.

Figure 11 is aside view of one of the contact i5 members shown in Figure 10.

Figure 12 is a view of the holder carrying th contact members of Figure 11.

Figure 13 is a fragmentary sectional view of a the contact device shown in Figof `one of the conrheostat support member such as shown in Fig- 20- ure 8, but showing a modified form of-stationary contact vmember for cooperation with the movable contact. y I

Figure 14 isa plan view ofthe auxiliary ccnwtact member shownin Figure 13.

Figure 15 is a fragmentary view of the method of mounting the rheostat to a mountingplate or support panel. This view is very similar to the part shown in Figure 9.

Figure 16 is a perspective view of the locking 30 mounting member shown in Figures 9 and 15. Figure 1'1 is a fragmentary view of the mounting panel to cooperate with the locking member shown in Figure 16.

Flgure\ 18 illustrates a modified form of stop 35 means for the rheostat contact arm.

Figure 19 isla sectional view throimh the contact arm endgfof a still further modified form 0f lrheostat.

port member having a base portion 2 and a centrai hub portion l with'a sector 4 extending thereentirely covered, except for a brush track surface l, with a vitreous enamel; 9- which also acts Y*to cement or anchor the unit, compris-v In `the variousviews of the drawingfl is a sup- 40 vio " trical contact thereto.

ing the wire and form 5, to the base portion 2 of the support member I. The method of preparing-the resistance unit per se is preferably as shown and described in Crouse Patent 1,880,239, issued .October 4, 1932, and need not befurther described herein.

The hub 3 of the support member carries an annular contact member III which is arranged concentrically and spaced a distance within the inner periphery of the circular form 5 carrying the winding. The contact member III is fastened to the upper surface of the hub 3 in any satisfactory manner as by a plurality of downwardly bent lugs I-I which pass into small openings in the end of the hub which are preferably `filled with cement and which, on setting, anchor the member III securely in place. The member III is provided with a terminal I2 for making elec- Preferably the terminal I2, in extending radially Ifrom the contact member I0, is positioned between a pair of positioning lugs I3 which project slightly upward from the upper surface of the sector 4, thereby assisting in holding the member III securely in operative position.

The hub 3 has a central hole therethrough and in this hole is positioned a sleeve I4 having a collar I5 at one end, engaging a shoulder adjacent one end of the hole. The other end of the sleeve I4 is threaded at I6 and provided with a nut I1 to securely lock the sleeve in position in the hub. An operating shaft I8 is positioned in the sleeve I4 by means of a pin I9 carried by the shaft I8 adjacent the collar I5, and a lock ring 20 carried in a groove in the shaft I8 adjacent the threaded end I6 of the sleeve I4. The pin I9 also acts as a stop for the rotary movement of the shaft by engaging the inner projecting parts 2| of the sector 4.

The end of the shaft I8 adjacent theannular contact member III, carries an arm 22 which is preferably of resilient metal and which arm is securely attached to a collar 23 which is preferably fastened to the shaft I8 by one or more set screws 24, two being illustrated in Figure 1.'v

The arm 22 has an orifice at its free end and this oriiice, in the form of rheostat shown in Figures 1 to 7, is in the shape of an elongated slot 25. The slot 25 is adapted to receive a similarly shaped projection 26 extending from one sidel of a holder 21 comprising part of a contact device. However, the holder 21 is made of strong insulating and preferably heat-resisting material of a ceramic nature, and has on the side, as shown in Figure 5, an arcuately formed seat 28 adapted to receive a curved lug 29 on one face of a contact device 30 which is preferably of a metal of good conducting quality, such as copper or a composition thereof.

As clearly shown in Figures 4 and 5, two members 30 are utilized and are heldin place by the side members 3I and 32. It will be noted that the members 38 are loosely and freely carried in the holder 21 which itself is more or less ilexibly carried on the flexible arm 22, and when the parts are assembled Aas shown in Figure 3, the contact devices 30 extend or bridge across the annular contact member I8 to the track surface 3 of the winding, it being understood that ther track surface 8 and the surface of the annular contact member I8 are substantially inthe same plane. However, by reason of the construction described, if one of the convolutions of the winding should extend slightly above its ynext adjacent one, the member 3l being free 'to oscillate in the holder 21 as described, will readily move as indicated in Figure 4 to take up the necessary alignment, whereby a good contact is insured at both ends of the members 30. The tension of the contacts between the winding and the member I8 is initially obtained by adjusting the collar 23 carrying the arm 22 on the shaft I3, by reason of the set screw 24.

In the form of rheostat shown in Figure 8, the construction is very similar to that already described, except that in this form the support member I is provided with an annular groove 39 within the body of the support I, and this annular groove carries the form 5 and the winding,

being anchored in the groove by the vitreous enamel 9. In addition, the arm 22 is riveted to the end of the shaft I8 and the pressure on the contact device to be described is obtained by giving the arm 22 the proper set, it being understood that the length of the shaft is such as to bring the arm 22 in substantially operative position after it has been riveted to the end of the shaft.

In this form of rheostat, the contact device is somewhat diierent from that previously described, in that it comprises a circular holder 33 having an extension with a flat side 34 to fit a correspondingly shaped hole in the arm 22. Furthermore, the arcuately formed seat 28 is of a little different shape than that shown in Figure 5, and likewise the contact members 35 are shaped differently from those shown in Figure 6, but they operate in the holder 33 to produce the same result as the construction shown in Figures 4, 5, and 6.

In Figure 13, the support member I, which is substantially the same as that shown in Figure 8, carries a contact member 31 constructed of a flat strip of metal bent around as shown in Figure 14 and fitted edgewise into an annular slot provided in the support member I, being anchored therein by suitable cement. In addition, the stop member may consist of a U-shaped member 45 set in the support I in the manner as illustrated in Figure 18, and in which the edge of the holder 33 will strike either one of the arms of the U-shaped member 45.

An important feature of our invention is the method of mounting the rheostat on the panel or supporting plate, and we have provided means by which the rheostat may have a single hole mounting; that is to say, the same hole which is drilledto receive the shaft also serves for mounting the rheostat on the panel. In such a mounting it is quite essential that the operation of the knob carried on the end of the shaft I3 will not turn the rheostat, and to absolutely prevent this taking place, we have provided a locking disc 38 adapted to fit over the threaded portion I6 of the sleeve I4, being positioned against the sleeve locking nut I1. The disc 38 has a lug 39 extending 4into a recess 48 in the support member I.

In addition, the disc 33 has two fingers or projections-4I that are adapted to enter holes 42 in the mounting panel 43, so that when the panel lockingnut 44 is screwed up on the threaded end Ii of the sleeve I4, the rheostat is locked securely in position on the panel through the locking disc 3l.

From the constructions so far described, It will be seen that the arm 22 carries no current and forms no part of the electrical circuit through the rheostat, the current coming in, for example, by way of the terminal I2 and itscon- 15 springs are required in' connection with the shaft i8 to puttension on the contactmembers.'

`Figure 19 shows a sectional view through one end of the .rheostat in which the resistor is carried in the support member I and connections made thereto as shown in Figure 8. Likewise,

1j the device is provided with an annular ring memberl'l substantially -as lshown .in Figure 13.

l However, the shaft i8 cames an insulator 46' which is fastened thereto in any .satisfactory manner as by pin 41. 'Ihe insulator 48 carries a circular contact member 48 which has a depression 49 in continuum nular member 81.

Preferably diametrically opposite to the depressed portion 49 the annular member is provided -with a projection or finger 50 which is in continuous engagement with the track surface 8 on the resistor. contact member has a spaced a distance fromthe insulator for the Purpose of promoting the flexibility of the contact member.

It. will thus be seen in this particular form that while the contact arm itself carries current, no current passes through the shaft or any extraneous spring. n

From what has been said, it will be understood that certain of the detalls for carrying our invention into practice may be varied to some extent, but such variations should come within the scope of the appended claims.

What we claim is: x

1. In a rheostat, a support member, a circular form of heat-resisting material having a winding thereon and means for fastening said winding to the support member, a part ofthe surcontact with the anface of said winding being exposed to form a brush track, an annular contact member concentrically carried on said support member` adjacent said winding, an arm concentrically mounted for rotation with respect to said form and winding, an insulator carried at the free end of said arm, and a current-carrying device carried by said insulator so as to simultaneously engage both the said annular contact member and said brush track on the winding'. said rheostat being further characterized in that said arm insulator has a proj ection on one side for engagement with said arm, and an arcuately formed seat on the opposite side, and at least one contact device oscillatably carried in said seat.

2. Ina rheostat, asupport member, a circular form of heat-resisting material having a winding p thereon and means for fastening said form and winding to the support member, a part of the surface of said winding being exposed to form a brush track. an annular cf ntact member concentrically carried on said support member adjacent said winding, an arm concentrically mounted for rotation with respect to said form and winding, an insulator carried at the free end of said arm, and a current-carrying device carried by said insulator so'as to simultaneously engage both the said annular contact member and said brush track on the winding, said rheostat being further characterized in that said arm insulator has a projection on ole side for engagement with said arm, and an arcuately formed seat on the opposite side, and a plurality of contact devices carried in said seat so they can have local inde-9 pendent movement.

form and means for engaging said support, vand means car- 3. In a rheostat, a support member.I a circular form ofheat-resisting material having a winding thereon and means for fastening said form and winding to the support member, a part of the surface of said winding being exposed to form 5 a brush track, an annular contact member concentrically carried on said support member adjacent said winding, an arm' concentrically mounted for rotation with respect'to said form and winding, an insulator carried at the free end of said 10` irregularities in the winding track. Preferably the circular pair of arcuate slots il 4. In a rheostat, a support member of heatlresisting insulating material, a circularcore of heat-resisting-material having a winding thereon,

-said winding and core being covered, except for 25 l one exposed side, with a vitreous enamel which also acts toianchor the winding and core to said support member, an annular contact ringconcentrlcally mounted on said support member within the inner periphery oi'- said. winding and 30 substantially on the same plane as the exposed side of said winding, a metallic arm concentrically mounted for rotation with respect to said winding, a contact holder of insulating material on the end of said arm and formed to provide a seat for a contact shoe, and at least one contact shoe loosely and oscillatably nested in said seat of said holder to maintain a continuous engagement with said exposed part of the winding and o said annular contact ring.

5. In a rheostat having a frame, a threaded bearing sleeve having a nut to clamp the sleeve to the fratrie. an operating shaft extending through the sleeve, means for mounting the rheostat on `a panel, comprising a hole through the panel for said shaft and sleeve, a plate initially loose and removable on the sleeve and having a A nger adapted to enter a recess in the rheostat frame, at least one projection extending from the plate in the opposite direction to, said linger into the panel, and a nut on the sleeve on one side of the panel to draw the rheostat and plate against the opposite side of the panel.

6. In a rheostat having a`threaded bearing Vl ent of the rheostat, per se, for. preventing said rheostat from turning on'the support, compris- 7o ing a separable plate located concentrically en lthe threaded part of the sleeve and between the rheostat and support, said plate having means to engage a part of the rheostat, and further ried on the sleeve to clamp said rheostat and plate securely against said support.

8. In a rheostat, a support member oli-insulating material, a circular core having a winding thereon with means for fastening the core to the support, at least the core being of high heatresisting material, the winding and core being covered, except for the top free edge of the winding, with a vitreous enamel coating, an annular contact ring carried on said support member ooncentrically with the winding and substantially on the same plane as the exposed top edge of the winding, an arm concentrically mounted for roltation with respect to the winding and carrying nested in said seat of said holding means to maintain a continuous engagement with said exposed part of the winding and said annular contact ring.

FRANK w. MCDONEIL. VICTOR L. osaoon. 

